Conventional approaches to Global Positioning System (GPS) frequency tracking are based on independently tracking signals from corresponding satellites with fixed bandwidth loop architectures. Typically, a first or second order loop filter is used to separately estimate the Doppler frequency shift and perhaps the Doppler rate for each signal from a sequence of error detections performed for the corresponding satellite. While it is possible to adapt each loop filter to the environment of each satellite, each channel must track the GPS oscillator error rate.
U.S. Pat. No. 5,343,209 entitled “Navigation Receiver With Coupled Signal-Tracking Channels” to Sennott discloses a GPS navigation receiver with coupled-tracing channels that periodically estimates frequency, phase and the other characteristics of received carrier signals utilizing estimated parameter measurements for a plurality of the received signals combined in a statistically appropriate manner that takes into account line-of-sight paths, receiver clock dynamics, and other considerations. The method of Sennott uses a carrier phase parameter, which requires tracking carrier phase.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.